Biological buffer

We describe here the ionization equilibria that account for buffering, and we show the quantitative relationship between the pH of a buffered solution and the pKa of the buffer. Biological buffering is illustrated by the phosphate and carbonate buffering systems of humans. 

Accuracy and precision runs concentrations> pg/mL in <protein buffer, biological matrix> >N runs... 

Covalent extraction PBA-phenyl boronic acid Covalent Vicinal diols Aqueous Alkaline buffer Biological fluids Acidic buffer Acidic methanol... 

Aminomethyl propanol buffer, biological blotting techniques 3-(Cyclohexylamino)-propanesulfonic acid 3-[4-( Hyd roxyethyl)-1 -pi perazi nyl]-propanesulfonic acid 3-(N-Morpholino)-propane sulfonic acid Sodium 3-morpholino propane sulfonate 3- Tris-(hydroxymethyl)-methylamino]-propanesulfonic acid buffer, biological cell cultures 3-(Cyclohexylamino)-propanesulfonic acid 3-[4-(Hyd roxyethyl )-1 -pi perazi nyl]-propanesulfonic acid 3-(N-Morpholino)-propane sulfonic acid Sodium 3-morpholino propane sulfonate 3- Tris-(hydroxymethyl)-methylamino]-propanesulfonic acid... 

This difference in behavior for acetic acid in pure water versus water buffered at pH = 7 0 has some important practical consequences Biochemists usually do not talk about acetic acid (or lactic acid or salicylic acid etc) They talk about acetate (and lac tate and salicylate) Why Its because biochemists are concerned with carboxylic acids as they exist in di lute aqueous solution at what is called biological pH Biological fluids are naturally buffered The pH of blood for example is maintained at 7 2 and at this pH carboxylic acids are almost entirely converted to their carboxylate anions... 

Table 8.19 pH Values of Biological and Other Buffers for Control Purposes 8.110... 

Lyophilization. LyophiLization is essentially a drying technology. Some dmgs and biologicals are thermolabile and/or unstable in aqueous solution. Utilization of freeze drying permits the production of granules or powders that can be reconstituted by the addition of water, buffered solution, or mixed hydrophilic solvents just prior to use, eg, certain antibiotic suspensions. 

Until the early 1960s, laboratory iavestigators rehed on dialysis for the separation, concentration, and purification of a wide variety of biologic fluids. Examples iaclude removal of a buffer from a proteia solution or concentrating a polypeptide with hyperosmotic dialysate. Speciali2ed fixtures were sometimes employed alternatively, dialysis tubes, ie, cylinders of membrane about the si2e of a test tube and sealed at both ends, were simply suspended ia a dialysate bath. In recent years, dialysis as a laboratory operation has been replaced largely by ultrafiltration and diafiltration. 

Biological activity (BA) was chosen as such parameter. The BA determined using a system and a technique for a class of natural polyphenolic bonds nicotinamide adenine dinucleotide restored (NAD H ) - ferricyanide (KjFe(CN)g) in a phosphates buffer solution. 

A biologically important point is revealed by the basic shape of the titration curves of weak electrolytes in the region of the pK, pH remains relatively unaffected as increments of OH (or H ) are added. The weak acid and its conjugate base are acting as a buffer. 

In acidic solution at low pH, a carboxylic acid is completely undissociated and exists entirely as RCO2H- In basic solution at high pH, a carboxylic acid is completely dissociated and exists entirely as RC02 - Inside living cells, however, the pH is neither acidic nor basic but is instead buffered to nearly neutral pH—in humans, to pH = 7.3, a value often referred to as physiological pH. In what form, then, do carboxylic acids exist inside cells The question is an important one for understanding the acid catalysts so often found in biological reactions. 

This relation, known as the Henderson-Hasselbalch equation, is often used in biology and biochemistry to calculate the pH of buffers. Historically, it was Henderson who discovered Equation 14.1 in 1908. Hasselbalch put it in logarithmic form eight years later. 

The poor solubility of coelenterazine in neutral aqueous buffer solutions often hampers the use of this compound in biological applications. The simplest way to make an aqueous solution is the dilution of a methanolic 3 mM coelenterazine with a large volume of a desired aqueous buffer solution. If the use of alcoholic solvents is not permitted, dissolve coelenterazine in a small amount of water with the help of a trace amount of 1 M NaOH or NH4OH, and then immediately dilute this solution with a desired aqueous buffer solution. However, because of the rapid oxidation of coelenterazine in alkaline solutions, it is recommended that the procedure be carried out under argon gas and as quickly as possible. 

Fig. 10.4.2 The effects of temperature (left panel) and pH (right panel) on the peak intensities of the Balanoglossus luminescence reaction. In the measurements of the temperature effect, 0.5 ml of 0.176 mM H2O2 was injected into a mixture of 1.2 ml of 0.5 M Tris buffer (pH 8.2), 0.3 ml of luciferase, and 1 ml of luciferin, at various temperatures. For the pH effect, the Tris buffer (pH 8.2) was replaced with the Tris buffers and phosphate buffers that have various pH values, and the measurements were made at room temperature. From Dure and Cormier, 1963, with permission from the American Society for Biochemistry and Molecular Biology.

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